Multipath magnetic core memory devices



Aug. 4, 1959 F. POST 2,898,581

MULTIPATH MAGNETIC CORE MEMORY DEVICES I Filed Nov. 19, 1956 4Sheets-Sheet 1 FIG..L FIG.2

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MULTIPATH MAGNETIC CORE MEMORY DEVICES Filed Nov. 19, 1956 4 Sheets-Sheet 2 F|G.3 1O

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Aug. 4, 1959 I F. L. POST 2,898,581

MULTIPATH MAGNETIC com: MEMORY DEVICES Filed Nov. 19, 1956 4Sheets-Sheet 4 READ DRIVER SENSE AMPLIFIER United States PatentMULTIPATH MAGNETIC CORE MEMORY DEVICES Frederick L. Post, Poughkeepsie,N.Y., assignor to International Business Machines Corporation, New York,N.Y., a corporation of New York Application November 19, 1956, SerialNo. 623,174

20 Claims. (Cl. 340-174) This invention relates to magnetic memorydevices and more particularly to improvements in such devices whichrender them particularly adaptable for use in high speed and/ornondestructive interrogation memory systems of the coordinate arraytype.

It is usual, in memory systems employed commercially, to arrange theindividual memory elements in the form of an array which is addressed byapplying signals to coordinate column and row drive lines. Any memoryele ment in such an array may be selectively addressed for reading orwriting by coincidently pulsing both the coordinate row drive line andthe coordinate column drive line with which it is associated. Many sucharrays utilizing magnetic cores as storage elements have beenestablished in the art. In meeting the stringent requirements made ofmemory by high speed computing devices, various magnetic elements havingcharacteristics particularly adaptable to etlicient use in high speedarrays have been developed. One such element is described in thecopending application Serial No. 546,180 filed November 10, 1955, andanother in copending application 564,530 filed February 9, 1956, both ofwhich applications have been assigned to the assignee of the presentapplication. Both these applications are by this reference theretoincorporated herein as part of this disclosure. The elements describedin each of these applications have come to be termed multipath cores andin operation flux changes are selectively accomplished in different onesof the flux paths encompassed within the cores.

One advantage which may be realized with cores of this nature is theiradaptability to operation at exceedingly high speeds in coordinate arraysystems wherein it is required that the prescribed flux reversals beexperienced in certain of the flux paths of a particular core only whenboth of the coordinate drive windings associated with that core arecoincidently energized. Core structures having this advantage are shownand described in the above-mentioned application Serial No. 546,180. Afurther advantage evidenced by the core structures of this applicationlies in the fact that the half select current pulses applied to thecoordinate drive windings are not limited in magnitude by a threshholdvalue as is the case in previous array systems. Another advantage whichmay be realized with cores of this nature is that only a small backelectromotive force is developed by windings on nonselected cores when acore in the same column or row is selected during a reading or writingoperation. A core structure embodying this advantage is shown in theaforementioned application Serial No. 564,530. This application alsodiscloses the manner in which, utilizing such a core, nondestructiveinterrogation may be realized,

A primary object of the present invention is to provide an improvedmultipath magnetic core element having a novel arrangement of drive andsense windings.

A further object is to provide a multipath magnetic core element whichis capable of being operated at exceedingly high speeds in largecoordinate arrays without there being the need of either supplying tothe coordinate drive lines power of the magnitude heretofore required byhigh speed arrays of this type, or of accurately controlling, withinsmall limits, the magnetizing force applied by a half select pulse toany core in the array.

A further object is to provide an improved core storage element having anovel arrangement of windings which, in accordance with a novel mode ofoperation, is capable of being interrogated in a nondestructive manner.

One form of the improved device, particularly adapted for high speedoperation, comprises a multipath core structure wherein information iswritten and then read out by applying magnetomotive forces to selectedones of the flux paths to thereby cause changes in flux in a localizedportion of the core material which is linked by a sense Winding. In thisembodiment, one portion of the core is divided into two major parallelflux paths of equal cross section and each of these flux paths issubdivided into two minor parallel flux paths which are also of equalcross section. The core is provided with a read winding which embracesonly one of the minor flux paths and a write winding which embracesanother one of the minor flux paths. Each of these windings, whenenergized, applies unidirectional magnetomotive force to the embracedpath and, since each winding embraces only one flux path, these pathsmay be normally subjected to a biasing magnetomotive force which helpsto control the shifting of flux in the localized paths during thereading and writing operations. A further advantage realized is that,because of the presence of the bias winding, coordinate read and writewindings may be utilized and driven by currents greatly exceeding thelimit normally established by the threshold of the magnetic material.Since currents greater than those normally allowable in half selectcoincident current systems may be utilized, the speed of switching maybe greatly increased, and this advantage is gained without the necessityof switching flux in any portion of the core when only one of the drivewindings is energized. As a result high speeds are attainable in largearrays of cores of this type without the necessity of providing a largeamount of power to switch localized flux paths in nonselected cores inselected rows and columns.

In another embodiment, the multipath core structure is shown with thewindings necessary to render it capable of being interrogatednondestructively. In this embodiment information is written in the coreby energizing write winding means effective to establish a remanentcondition in one or the other of two opposite directions in the mainflux paths of the core. The core is then conditioned for interrogation.Interrogation, itself, is a two step operation, the core first being setup by pulsing a setup winding means which embraces one of the minor fluxpaths and then read out by pulsing a read winding means which embracesanother of the minor flux paths. The setting up and reading out of theinformation in the core involve only localized flux changes, the overalldirection of the main flux remaining the same. As a result, the core maybe interrogated repeatedly without destroying the information storedthereon.

There is also shown an array of cores capable of nondestructiveinterrogation. Each of the cores in the array is provided with row andcolumn coordinate write windings and with row and column coordinatesetup windings. The selection of a particular core in the array to beinterrogated is accomplished by coincidently energizing the proper rowand column setup drive lines. The read windings on each core in thearray may be connected to a common signal source since the applicationof a read pulse will cause only a previously set up core to beinterrogated.

Thus another object of the invention is to provide improved high speedand nondestructive multipath magnetic storage elements wherein thevarious drive windings need embrace only one of the core flux paths,thereby greatly simplifying the problem of assembly of high speed andnondestructive core arrays.

A further object is to provide core elements of this type which may bedriven by half select pulses applied to each of two drive windings, andwherein the application of a half select pulse to one drive windingsalone does not cause a flux reversal in the core so that the pulsedwinding then presents a relatively low impedance to the pulse suppliedby the coordinate drive line.

Another object is to provide a magnetic memory element wherein binaryinformation values are represented by different patterns of fluxdistribution in localized flux paths in the element, and wherein biasmagnetizing forces applied to certain of these flux paths aids in theshifting of flux from one of the flux path to the other and also rendersthe core adaptable for use in coordinate high speed memory arrays.

A further object is to provide a magnetic memory element having oneportion thereof divided into four parallel flux paths whereininformation is stored and the element interrogated by selectivelyshifting flux from between the different paths.

A further object is to provide a coordinate memory array employing astorage element capable of being repeatedly interrogatednondestnictively wherein each interrogation cycle involves only twooperations.

A further object is to provide such an array wherein the core to beinterrogated is selected by the selective energization of two coordinatedrive lines and the actual readout is accomplished by the subsequentenergization of a single read drive line.

These and other objects of the invention will be pointed out in thefollowing description and claims and illustrated in the accompanyingdrawings, which disclose, by way of example, the principle of inventionand the best mode, which has been contemplated, of applying thatprinciple In the drawings:

Figs. 1 and 2 are diagrammatic representations of different forms of thecore structure utilized in the present invention together with certainof the windings which render the core capable of high speed memoryoperation.

Figs. 3, 3A, 3B, 3C, 3D, 3E and 3F are diagrammatic representations of aportion of the structure of Fig. 1 which depict the various fluxpatterns established during the operation of the core.

Fig. 4 is a diagrammatic representation of a hysteresis loop for amagnetic material such as might be utilized in practicing the invention.

Fig. 5 is a diagrammatic representation of a portion of a magnetic coreelement, such as is shown in Fig. 1, and indicates one method ofpositioning windings through the various apertures to render the coreadaptable for use in a coordinate memory array.

Fig. 6 is a diagrammatic showing of a memory core structure togetherwith the windings necessary to store information in the core andinterrogate the core nondestructively.

Figs. 7A, 7B, 7C, 7D, 7E and 7F are diagrammatic representations ofdifferent flux patterns established in a portion of the core of Fig. 6during writing and interrogation operations.

Fig. 8 is a modification of the device of Fig. 6 and illustrates themanner in which half select drive windings may be positioned on a coreof this type in a coordinate array system capable of being interrogatednondestructively.

Fig. 9 is a diagrammatic representation of a two dimensional array ofmagnetic elements of the type shown in Fig. 7.

The basic form of the magnetic storage element may be toroidal as shownin Fig. 1, or rectangular as shown in Fig. 2 or may be of otherconfigurations. Equivalent apertures and windings shown in Figures 1 and2 are given similar designations, the description about to be given ofFig. 1 sufiicing to explain the structure of both figures. Core 10 ofFig. 1 has positioned therethrough an opening 12 which divides the righthand portion of the core into two sections or flux paths designated Aand B. The cross sectional area of the magnetic material in each ofthese flux paths may be equal to or slightly greater than that of theleft-hand portion of the core which is designated C. Paths A and B areeach further subdivided by a pair of openings 16 and 20 intosubstantially equal parallel flux paths, designated a, b, c, and d. Thecore 10 is provided with a first winding 14 which is positioned throughopening 12 to embrace flux path B. A second winding 15 is positionedthrough opening 16 to embrace flux path 0. A third winding 18 ispositioned through opening 20 to embrace flux path 11 and a furtherwinding 22 is provided which embraces the magnetic material in sectionC. The winding 22 is utilized only once to initially establish acondition of unidirectional flux remanence in the core, after whichwindings 14, 15, and 18, which are sense, write and read windings,respectively, are utilized to accomplish the operations necessary to thestoring and reading out of binary information. Winding 22 is initiallyenergized by a signal source 24 thereby causing a clockwisemagnetomotive force to be applied to the core. When the signal appliedto winding 22 is terminated the core assumes a remanent state with theflux orientated in the clockwise direction. Since the cross sectionalarea of section C is approximately equal to or less than that of A andB, the flux orientation established is as indicated by the fluxdirection lines designated 26; the remanent clockwise conditionestablished being primarily confined, in the right-hand section of thecore, to the shorter flux path A. After winding 22 is energized toestablish this condition, it is no longer employed. In the abovedescribed operation, the smaller cross section of the portion C, whichis embraced by winding 22, serves to quantify the amount of fluxorientation. which is accomplished in the other portion of the coreincluding paths A and B when this winding is energized. However, such ageometry is not a necessity since the amount of flux reversal achievedmay be also quantified in other ways, for example, by quantifying theenergizing signal applied to the core, in which case the core may have auniform cross section throughout. For a more detailed discussion of thistype of quantification, reference may be made to copending applicationSerial No. 613,952, filed on October 4, 1956, and assigned to theassignee of this application.

Fig. 3 shows, in somewhat enlarged form, the righthand portion of thecore 10, together with the sense, read and write windings which embracesflux paths in this portion of the core. The initial condition of fluxremanence established by energizing winding 22 is indicated by thedotted flux lines 26 in flux paths a and 12. Read winding 18 isconnected to a signal source 30 and write winding 15 is connected to asignal source 32. After the initial remanent condition is established,each of the signal sources is controlled to normally maintain a biascurrent flowing in the winding to which it is connected. The directionof bias current flow is indicated by the arrows on windings 18 and 15.When the bias currents are ini tially established, winding 18 applies tothe embraced path 11 a downward magnetomotive force as is indicated bythe arrow 34. Since this applied force is in the same direction as theinitial remanent orientation in flux path b, there is no flux reversaleffected; the bias current merely serving to maintain this portion ofmagnetic material in a saturated condition in the direction of arrow 34.However, when the bias current is established in winding 15, in which noflux orientation has been previously accomplished, the magnetomotiveforce applied in the direction of arrOW 35 causes the flux in alocalized area around opening 16 to be driven to a saturation conditionin a counterclockwise direction .as is indicated by the fluxrepresenting line 36 in Fig. 3A.

Flux lines 26 and 36 in Fig. 3A represent the initial condition of thecore material including the flux paths embraced by the read, write andsense windings before functional circuit operation is begun. There isshown in Fig. 4 a hysteresis loop such as is obtainable by plottingmagnetic flux density B versus magnetic field intensity H for a magneticmaterial such as might be utilized in the core 10. The oppositeconditions of remanent flux density are represented in Fig. 4 at x and yand the initial saturation condition of path b between openings 20 and12 and path 0 between openings 12 and 16 is represented at e.

The initial step in the operation of the circuit is to establish a datumcondition in the core material adjacent the openings. This isaccomplished by applying a pulse to winding 18 effective to causecurrent flow in the direction opposite to that of the bias current flowin this winding. The magnitude of the pulse is sufiicient to cause to beapplied to path I) a magnetomotive force equal in magnitude but oppositein direction to that applied as a result of the flow of bias currentthrough the winding. The change in the intensity of the magnetic fieldapplied to path b, when winding 18 is thus pulsed, is depicted in Fig. 4by an arrow designated H The field applied to path I; is in an upwarddirection and therefore tends to reverse the fiux in this path. Sinceflux in paths a and c is also oriented downward, and the fluxorientation is upward only in path d, the magnitude of the appliedmagnetomotive force must be suificient to switch the flux in a circularpath extending around both openings 12 and 16 as is depicted by thearrow 42. When such a field is applied, by applying a signal ofsufiicient magnitude to winding 18, the resulting flux distribution isas shown in Fig. 313; a condition of flux saturation in the clockwisedirection being established around opening 12; the remanent fluxcondition remaining essentially the same in path b; and the flux in themain path from section C (see Fig. l), which previously extended throughpath b, now being shifted to outer path a due to the increase of thereluctance to the remanent flux in path b caused by the establishing ofthe localized condition of saturation around opening 12.

When the input signal to winding 18 terminated, the bias current on thatWinding again takes effect, causing a downward magnetomotive force to beagain applied to path b between holes 12 and 20. This appliedmagnetomotive force is on the proper direction to cause a flux reversalon both sides of opening 29 thereby causing a localized condition offlux saturation in a clockwise direction to be established around thisopening thereby increasing the reluctance of path a and forcing the mainflux from path a to path c as is shown in Fig. 3C. The flux distributionshown in this figure represents a datum condition, which in operationmay be designated the zero representing condition.

Once this datum condition is established, a zero may be written in thecore by again pulsing winding 18 or by failing to pulse any winding. Theapplication of a pulse to winding 18 with the flux in the core materialdistributed as shown in Fig. 3A merely causes a flux reversal in thecircular path around opening 20 so that when the pulse is applied theflux distribution is as shown in Fig. 3F. Upon termination of the inputpulse the bias again takes effect and the core again assumes the fluxcondition shown in Fig. 3C.

When it is desired to write a binary one, a pulse is applied to winding15 to overcome the bias and cause current flow in the direction oppositeto that indicated by the arrow on this winding. The operation is similarto that described above with respect to the change in flux distributionwhen winding 18 is pulsed with the core in the condition shown in Fig.3A. The pulse applied to winding 15 is sufiicient to cause a change inthe intensity of the magnetic field applied to path 0 such as isindicated at H in Fig. 4. As a result, as is shown in Fig. 3D, alocalized clockwise condition of flux saturation is established in thematerial around opening 12 and a portion of the main flux is shiftedfrom path c to path a. When the signal on winding 15 is terminated, thebias again takes effect causing a downward magnetomotive force to beapplied to path 0. Since the direction of the main flux then in path dis also downward, the magnetomotive force applied, as the bias currentis re-established in winding 15, causes a condition of flux saturationto be established around opening 16 and the main flux in path d to beshifted back to path b. The resulting flux distribution is shown in Fig.3E and this condition of flux distribution is designated the binary onerepresenting condition.

The state of the core may be interrogated by pulsing winding 18 in themanner described above. The output signals are developed on sensewinding 14, which, as shown in Fig. 3, embraces all of section B and istherefore responsive to flux changes in paths 0 and d. When a binaryzero has been stored in the core and it has thus been caused to assumethe condition of flux distribution shown in Fig. 3C, the application ofa signal to read winding 18 causes only a localized flux reversal aroundopening 20, the change in flux distribution being from that of Figure 3Cto that of Fig. 3F, and thus no output is induced on sense winding 14.Upon termination of the read pulse on winding 18, the bias current againtakes effect and the core again assumes the zero representing conditionof Fig. 3C.

When, after the core has been caused to assume the binary one conditionof Fig. 3E, a read pulse is applied to winding 18, the flux distributionchanges from that of Fig. 3E to that of Fig. 3B. This involves areversal of the flux in the magnetic material in path d which isembraced by sense winding 14 and an output signal is then induced in thesense winding. Upon termination of the read pulse the bias current onwinding 18 takes eifect and the Core assumes the zero or datumrepresenting state of Fig. 3C. The readout operation is thus destructivein that it destroys the information stored in the core.

It should be noted that the bias applied to paths 1) and c may besupplied by separate bias windings embracing these paths in which casethe windings 18 and 15 are energized only during reading and writingoperations. Where separate bias windings are utilized, which as abovenormally maintain paths [2 and c at the saturation condition 2 of Fig.4, the magnitude of a signal individually applied to either of thewindings 18 and 15 must, of itself, be sufficient to render theconnected winding effective to overcome the bias magnetic fieldintensity and apply a field greater than the coercive field shown at Hin Fig. 4, to the embraced path.

Fig. 5 shows the manner in which separate bias windings might be woundand also illustrates the manner in which coincident current reading andwriting may be achieved. In the construction of Fig. 5,, the biasmagnetomotive is applied to paths b and c by windings and 52,respectively. Current is caused to continuously flow in these windingsin the direction shown so that paths b and c are normally subjected to amagnetomotive force in the downward direction and the magnetic materialin these paths between opening 29 and 12, and between 12 and 16 isnormally in the saturation con dition represented at e in Fig. 4. Readpulses are applied by the coordinate read windings 18x and 18y and writepulses by the coordinate write windings 15x and 12y. Outputs aredeveloped as before in sense winding The signals applied to thecoordinate read and write windings are sufiicient to apply a magneticfield, in intensity equal to H shown in Fig. 4, to the embraced path. Asis indicated in Fig. 4 the application of a signal 7 to any one of thesewindings alone is not sufiicient, in the presence of the bias field, tocause the coercive field H to be exceeded. Thus the application of asignal to either read winding alone or to either write winding alone isineffective to cause a flux reversal and causes a flux change, in theembraced path, represented by the segment e.g., which flux change, dueto the flatness of this portion of the loop, is relatively small. Upontermination of such a signal the embraced path reassumes the biasedsaturation condition at e. The flux distribution is thus unchanged bythe application of a signal to either of the coordinate read or writewindings alone. However, where both read windings 18x and 18y are pulsedcoincidently, or where both write windings are pulsed coincidently, thetotal intensity of the magnetic field thereby applied is as shown at 2Hin Fig. 4. The application of such a field overcomes the bias and causesthe coercive field H to be exceeded so that changes in flux distributionare accomplished in the same manner as described with reference to Figs.3, 3A, 3B, 3C, 3D, 3E and 3F, wherein windings 18 and 15 are utilized toaccomplish reading and writing.

In both of the embodiments of Fig. 3 and Fig. 5, it is possible toemploy cores of a magnetic material which does not necessarily exhibit asquare type hysteresis loop, as indicated by dotted representation gh ofFig. 4, as long as the ratio of flux density at remanence to that atsaturation is relatively high. Further, since as explained above, withreference to Fig. 5, the application of a signal .to either of thecoordinate read or write windings alone does not involve a flux reversalin any part of the core and thus the back electromotive force developedby these windings is relatively small during half select operation. Forthis reason, it is possible to drive coordinate read and write windings,in a coordinate array of cores constructed as shown in Fig. 5, with arelatively small amount of power. Further, since it is possible toemploy biasing fields with the core construction of Fig. 5 extremelyhigh speeds may be achieved in coordinate array systems using cores ofthis type. It is only necessary that the intensity of the biasing fieldand the intensity of the field applied by each coordinate drive lineindividually be so related that coincident energization of both drivelines are required to cause a flux reversal. Regardless of the magnitudeof the fields employed, and the speed thus achieved, there is no fluxreversal in the core unless both drive lines are coincidently energized,and thus power requirements remain relatively low. At the same timeregardless of the magnitude of the fields employed and speed achieved,there is little or no flux change experienced in the portion of the corematerial embraced by the sense winding when a binary zero is read outand the signal to noise ratio remains exceedingly high.

Fig. 6 shows a further embodiment of the invention which utilizes a core10 having the same configuration as that of the previously describedembodiment and the core and apertures therein are identified by the samereference characters. The core of this embodiment is shown to beprovided with four windings designated 62, 64, 66 and 68 so adapted thatthe structure is capable of storing binary information and of beinginterrogated in a nondestructive manner. Winding 62 embraces section Cof the core 10 and is a drive winding which is employed to writeinformation in the core. A binary one is written in the core by pulsingwinding 62 with a signal of a polarity and magnitude effective toestablish a remanent flux condition in the counterclockwise condition inthe principal flux path around the core. As before, this remanentcondition is, in the main, confined to the inner section A of the righthand portion of the core 10. A binary zero is written in the core bypulsing winding 62 with a pulse of opposite polarity to establish aremanent condition of flux density in the clockwise direction.

Winding 64 is threaded through openings 12 and to embrace flux path band is termed a setup winding which, when energized, conditions the corefor nondestructive interrogation. Winding 66, which is the read windingand is positioned through openings 12 and 16 to embrace flux path 0, isthen energized to cause an output indicative of the state of the core tobe manifested on sense winding 68 which, as shown, is also positioned toembrace the magnetic material in flux path 0 between openings 12 and 16.

The changes in flux distribution effected during nondestructiveinterrogation of the core, when in the binary zero representation state,are shown in Figs. 7A, 7B, and 7C and the changes in fiux distributioneffected during the nondestructive interrogation of the core, when in abinary one representing state, are shown in Figs. 7D, 7E and 7E. After abinary zero has been entered in the core, the flux distribution in theportion of the core embraced by the sense, read and set windings is asshown in Fig. 7A, paths a and 11 having been caused to assume a remanentcondition of flux density in the direction shown by pulsing winding 62with a pulse of proper polarity. The core may be then conditioned forsubsequent nondestructive interrogation either by pulsing windings 64and 66 successively or merely by pulsing winding 66 alone. If setupwinding 64 is first energized to cause current flow in the directionindicated and thereby apply, as is indicated by an arrow 10 in Fig. 713,a downward magnetomotive force to the magnetic material in path bbetween apertures 20 and 12, no flux reversal is then effected since theapplied magnetornotive force is in the same direction as the remanentflux. The flux distribution therefore, remains the same, as is indicatedin Fig. 7B. If the read winding 66 is then energized to apply a downwardmagnetomotive force to path 0, in which no flux orientation has beenpreviously effected, a localized condition of saturation is establishedaround opening 16. The condition of flux distribution after energizingwinding 66 is shown in Fig. 7C. Thereafter, if setup winding 64 and readwinding 66 are successively energized, no output will be developed onwinding 68. Each energization of winding 64 causes magnetomotive forceto be applied to path b in the same direction as the remanent flux andtherefore the flux dis tribution remains as shown in Fig. 7C. Asubsequent energization of winding 66 merely drives the localized fluxpath around opening 16 from remanence to saturation causing only a smallflux change in path c and only an insignificant output to be induced onwinding 68. Once the core has been caused to assume the condition ofFig. 7C, it may be continuously interrogated without destroying theinformation therein, each interrogation cycle comprising the successiveenergizations of windings 64 and 66.

The condition of Fig. 7C may also be arrived at by merely pulsingwinding 66 after a binary zero has been written in the core. Such a readpulse might be applied to winding 66 following the write pulse duringeach write cycle or might be applied previous to the beginning of theinterrogation operations.

When a binary one has been originally written in the core, the fluxpattern is as shown in Fig. 7D. If we consider that, as above-mentioned,each write cycle includes both a pulse applied to write winding 62 and asucceeding pulse applied to winding 66, the flux pattern will be thesame as shown in Fig. 7D, with the exception that a localized conditionof flux remanence in the counterclockwise direction is establishedaround opening 16. Whether or not a read pulse is applied during thewrite cycle, the operation is thereafter the same, the flux distributionestablished during setup and reading being shown in Figs. 7E and 7F.Thereafter, any number of nondestructive read cycles may be undergone,each cycle comprising the application of a pulse first to set up winding64 and then to read winding 66. The first setup pulse, since it causesmagnetomotive force to be applied in a downward direction to theembraced path b, causes the magnetic material around opening 12 to besaturated in the counterclockwise direction and a portion of the mainflux to be shifted to path d. Upon termination of the setup signal, thecore assumes the remanent state of flux distribution shown in ig. 7E.The application of a pulse to winding 66 then causes a reversal of fluxin the path around opening 12 thereby causing an output to be induced insense winding 68, the core assuming a remanent condition of flux in thedirections shown in Fig. 7F, upon termination of the read pulse.Thereafter, each setup pulse applied to winding 64 drives the core fromthe condition of Fig. 7F to that of 7E and the subsequent application ofa read pulse to winding 66 causes the core to again assume the conditionof Fig. 7F. This operation involves only the reversing of flux in thelocalized path around opening 12 and each read pulse applied iseifective to cause such a flux reversal which results in an output beinginduced in winding 68.

Once binary information has been read into core of Fig. 6, and the coreconditioned for interrogation, the information bit stored may be readout any number of times nondestructively. The core may at any time bereset by pulsing winding 62 with a pulse of a polarity to establish aremanent condition in the clockwise direction in the main flux path,after which new information may be written by pulsing Winding 62 with apulse of the proper polarity, or, where a binary zero is to be written,merely by failing to pulse this winding. Since the readout of a binaryzero causes only a minor flux change in the localized flux path aroundopening 12 as it is driven from remanence to saturation, the signal tonoise ratio is high.

Fig. 8 shows another core configuration usable in magnetic circuitsoperated in accordance with the principles of the present invention. Thewindings on this core are adapted for writing and nondestructiveinterrogation in a coordinate array system. The principles of operationare the same as described with reference to Fig. 6, with the exceptionthat writing is now accomplished under control of two windings 62x and62y which are energized with pulses of a magnitude such that it isnecessary to energize both windings coincidently to write information inthe core. Similarly, the setup winding 64 of Fig. 6 has been replaced bycoordinate windings 64x and 64y, each of which, when energizedexclusively, is inetfective to cause a flux reversal but both of which,when energized coincidentally, eifect the same changes in fluxdistribution as are caused by the energization of winding 64 in theembodiment of Fig. 6.

Fig. 9 shows a two dimensional coordinate array of cores 10 wound in themanner of the embodiment of Fig. 8. Though only a two dimensional arrayis here shown and described, it is of course obvious that this arraymight serve as one plane in a three dimensional array wherein the X andY coordinate lines drive windings on cores in each two-dimensional planeof the array. Input informa tion is applied to the cores in the array ofFig. 9 under the control of three row signal sources 80a, 80b and 800and three column signal sources 82a, 82b and 820. These signal sourcesare controlled by address register circuitry not shown, to apply signalsto the coordinate row and column drive lines. For example, a coordinaterow drive line 84a is connected to row driver 86a so that each time thisdriver is actuated by the address register circuitry, a half selectpulse is applied to the input windings 62x on each of the cores 10 inthe top horizontal row. Similarly, a coordinate drive line 86a isconnected to column driver 82a so that signals, supplied by the driver,are applied to the input windings 62y on each of the cores 10 in theleft hand column. As was previously explained with reference to Fig. 8,it is necessary that both windings 62x and 62y on any core 10 becoincidently energized to Write information in that core. If we considerthat each of the cores is initially at remanence in the clockwisedirection, which is the binary zero representing condition, binary zerosmay be read into any one of the cores by either coincidently pulsing theproper X and Y drive lines, or failing to pulse these lines, with pulsesof the proper polarity. Binary ones may be written by coincidentlypulsing the proper X and Y drive lines with pulses of a polarity tocause reversal of flux in the principal core path from a clockwise to acounterclockwise condition. For example, information in the form of abinary one or a binary zero may be written in the core 10 in the upperleft-hand corner of the array by coincidently pulsing drive lines 84aand 86a. Once the required information is read into the cores in thearray, the array may be interrogated and, because of the nondestructivefeature, interrogation may be repeated as often as desired withoutdestroying the information .stored. The cores 10 may be conditioned forinterrogation by controlling a signal source 70, which may be termed theread driver, to supply a pulse to a read drive line 92 which drives theread windings 66 on all of the cores in the array. As previouslyexplained, impulsing the read winding causes the flux in the flux pathsA and B of cores storing a binary zero, and thus initially in thecondition shown in Fig. 7A, to assume a remanent condition as shown inFig. 7C. In the cores storing a binary one and thus initially in thecondition of Fig. 7D, the pulsing of line 92 merely orients the flux ina circular path around opening 16. Once the cores have been thusconditioned, they may be interrogated as described above, eachinterrogation consisting of a setup and then a read operation. Selectionof the core to be interrogated during each interrogation cycle is undercontrol of three row setup drivers 96a, 96b and 96c and three columnsetup drives 96a, 96b, and 960 which are in turn controlled by addresscircuitry not shown. The row setup drivers are connected to row setupdrive lines 100a, 1001) and 100c and the column step drivers areconnected to column setup drive lines 102a, 1021; and 1020. These setupleads drive the half select setup windings 64x and 64y on the variouscores 10. For example, column setup driver 98a drives line 102a which isconnected to each of the setup windings 64y on the cores 10 in theleft-hand vertical row of the array and row setup driver 86a drives line100a which is connected to each of the setup windings 64x on the cores10 in the top horizontal row of the array. After the selected core isset up by coincidently pulsing the proper setup drive windings, readdriver 90 is actuated causing an output indicative of the binary bitstored in the selected core to be developed on the sense winding 68 forthat core. The sense windings 68 on all of the cores in thearray areconnected to a sense amplifier so that, during each interrogation cycle,an output indication of the bit stored in the particularcoreinterrogated is transmitted to this amplifier.

Since it is required that both setup windings on any core becoincidently energized to render the core effective to cause an outputto be developed when the subsequent read signal is applied, it is onlythe core at the intersection of the pulsed setup lines which produces anoutput in response to the application of the read signal. For example,when, with a binary one stored in all of the cores in the left-handvertical column, setup windings 96a and 98a are coincidently energized,only the upper left-hand core in the array will be driven to thecondition of Fig. 7E. Thus, only the top core in the column experiencesa flux reversal when the read pulse is subsequently applied and it isthe output due to this flux reversal which is transmitted to senseamplifier 110. Neither half selected nor fully selected cores areeifected by the setup pulses when they are in the binary zero condition,since the magnetomotive force then applied to'the core material betweenopenings 20 and 12 is in the same direction as the remanent flux andthus no flux reversal is experienced. These cores, upon termination ofthe setup signals, reassume their initial flux state which is shown inFig. 7C. The subsequently applied read pulse merely drives the 10-calized paths around opening 16 in each of these cores from remanence tosaturation and cause no appreciable output to be developed in the sensewindings 66 on these cores.

Since the selection of the core to be interrogated is made by impulsingthe proper setup windings, the signal applied to the read windings 66may be as large as desired and thus an exceedingly high speed ofswitching during read-out may be realized. Further, though only a singleread line connected to all the read windings is shown in theillustrative embodiment of Fig. 9, several read windings might be used.For example, there might be one read winding for each row of cores.Where such a construction is utilized, the output signal to noise ratiomay be improved considerably over that usually attainable in coordinatearray systems by pulsing during each readout operation, only the readline for the row which contains the core to be interrogated.

After completion of the first interrogation operation, the same core maybe repeatedly interrogated by first coincidently pulsing drive lines100a and 102a and then pulsing read drive line 92. In a similar mannerany of the other cores in the array may be interrogated as often asdesired following the same sequence of operation. In each operation, thecore to be interrogated is first selected by pulsing the propercoordinate setup drive lines. The selected core is then read by pulsingthe read drive line 92.

It should be noted that, in the above-described mode of operation, theapplication of the setup signals during an interrogation cycle to aselected core in the binary one condition causes a flux reversal in thelocalized path around opening 12. This flux reversal causes an output,of a polarity opposite to that produced upon the subsequent applicationof a read pulse, to be transmitted to sense amplifier 110. Since a fluxreversal is accomplished around this opening with a core in the binaryone condition both upon the coincident energization of the setupwindings and the energization of the read windings, and since no fluxreversal is ever effected in a core in the binary zero condition by thesetup signals, the output of the array may be taken at the time thesetup windings are energized. Where this mode of operation is utilizedit is not necessary to initially condition the cores for interrogation,but interrogation operations may be begun immediately after theinformation is written in the cores in the array. Each interrogation isagain a two-cycle operation involving alternate energization of the readand proper setup drive lines and, according to the mode practiced,polarity sensitive or gating circuitry may be utilized in conjunctionwith the same amplifier circuitry to transmit only one of the outputpulses produced when a core in the binary one representing condition isinterrogated.

It should also be noted that, in each of the embodiments shown, binaryinformation may be represented by the presence or absence of the mainflux in one particular path or by the direction of flux in a particularpath. For example, all of the flux changes, depicted in Figs. 7A, 7B,7C, 7D, 7E and 7F, which are utilized in producing the desired outputsare experienced in paths b, c and d and the direction of fiux in path balone, after writing by windings 62, is indicative of the informationstored in the core.

It should be further noted that, in operating the core structures of thepresent invention, flux is never switched at any one time in a flux pathwhich encompasses more than two of the openings in the core. For thisreason the actual flux paths switched during any single operation arenot required, by the geometry of the structure, to be of such greatlength as to appreciably lessen the switching speeds.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the artwithout departing from the spirit of the invention. It is the intentiontherefore, to be limited only as indicated by the scope of the followingclaims.

What is claimed is:

1. In a magnetic circuit, a core of magnetic material capable of beingcaused to assume different remanent conditions of flux orientation, saidcore having a first portion and a second portion, the cross portion ofmagnetic material in said first portion being greater than twice aslarge as the cross section of magnetic material in said second portion,said first portion of said core having first, second and third openingspositioned therethrough dividing said core into four parallel fluxpaths, a first winding positioned through said first and second openingsonly, a second winding positioned through said second and third openingsonly; first and second signal means coupled to said first and secondwindings, respectively, for applying energizing signals thereto; and anoutput winding inductively associated with at least a portion of themagnetic material in said second portion of said core.

2. In a magnetic circuit, a core of magnetic material capable of beingcaused to assume different remanent conditions of flux orientation, saidcore having first, second and third openings therethrough dividing aportion of said core into first, second, third and fourth parallel fluxpaths, a first winding positioned through said first and second openingsonly to embrace only said second flux path, a second winding positionedthrough said second and third openings only to embrace only said thirdflux path, means coupled to said first and second windings for applyingenergizing signals thereto, and output Winding embracing at least one ofsaid third and fourth flux paths.

3. In a magnetic circuit, a core of magnetic material capable of beingcaused to assume different remanent conditions of flux orientation, saidcore defining a closed main flux path, the cross section of magneticmaterial in a first portion of said core being greater than twice aslarge as the cross section of magnetic material in a second portion ofsaid core, said first portion of said core having first, second andthird openings therethrough di- "iding said first portion into first,second, third and fourth flux paths of substantially equal crosssection, said first flux path being bounded by the inner periphery ofsaid main flux path and said first opening, said second flux path beingbounded by said first and second openings, said third flux path beingbounded by said second and third openings, said fourth flux path beingbounded by said third opening and the outer periphery of said main fluxpath, a first input winding embracing magnetic material in said secondportion of said core, a second input Winding embracing said second fluxpath only, a third input winding embracing said third flux path only,and an output winding embracing at least one of said third and fourthflux paths.

4. A magnetic core memory device comprising a closed magnetic circuitcapable of being caused to assume different remanent flux conditions,said circuit having a portion thereof divided into first, second, thirdand fourth parallel flux paths, means for establishing a condition ofremanent flux in at least a portion of said closed magnetic circuitincluding said first and second flux paths, input winding meansembracing said second flux path only and effective when energized with afirst signal to increase the reluctance of said second path only to saidremanent flux and thereby cause said remanent flux to traverse saidfirst and one of said third and fourth paths instead of said first andsecond paths, and an output winding embracing at least one of said thirdand fourth flux paths.

5. A magnetic circuit device comprising a core of magnetic materialcapable of being caused to assume stable conditions of flux remanence,said core defining a main fiux path, said main flux path comprising in afirst portion of said core first, second, third and fourth parallel fluxpaths, means for establishing a condition of unidirectional fiuxremanence in said rnain flux path wherein the remanent fiux traversessaid first and second flux paths in said first portion of said core;first winding means inductively associated with said second flux patheffective, when caused to apply magnetomotive force in a first directionto said second path, to cause said remanent flux in said main path totraverse said first and fourth paths instead of said first and secondpaths; said first Winding means being effective, when subsequentlycaused to apply magnetomotive force in an opposite direction to saidsecond fiux path, to cause said remanent flux in said main path totraverse said third and fourth flux paths instead of said first andfourth paths; means coupled to said first Winding means for causing saidwinding means to apply magnetomotive forces in each of said directionsto said second flux path, second winding means for causing said remanentflux in said main flux path to again traverse said first and second fluxpaths, and output winding means for sensing flux changes in at least oneof said four parallel fiux paths.

6. In a magnetic memory device, a core of magnetic material havingfirst, second and third openings positioned through a portion thereofdividing said portion into first, second, third and; fourth parallelflux paths, said core being capable of being caused to assume a firstremanent condition with flux oriented in a first direction in a closedpath extending around said core and including said first and second fluxpaths and a second remanent condition with flux oriented in said firstdirection in a closed flux path extending around said core and includingsaid third and fourth flux paths, first and second winding meansnormally applying bias magnetomotive forces in a first direction to saidsecond and third flux paths, respectively, pulse means coupled to saidfirst Winding means for rendering said first winding means effective toapply magnetomotive force to said second flux path in a directionopposite said first direction, signal means coupled to said secondwinding means for rendering said second winding means effective to applymagnetomotive force to said third fiux path in a direction opposite saidfirst direction, and output winding means inductively associated with atleast one of said parallel flux paths.

7, In a magnetic memory device, a core of magnetic material havingfirst, second and third openings positioned through a portion thereofdividing said portion into first, second, third and fourth parallel fluxpaths, said core being capable of being caused to assume a firstremanent condition with fiux oriented in a first direction in a closedpath extending around said core and including said first and second fluxpaths and a second remanent condition with flux oriented in said firstdirection in a closed flux path extending around said core and includingsaid third and fourth flux paths, first and second bias windingsapplying magnetomotive force in said first direction to said second andthird flux paths, respectively; means for controlling said core when insaid first remanent condition to assume said second remanent conditioncomprising a winding means embracing said second flux path and effectivewhen energized to overcome said bias magnetornotive force applied bysaid first bias winding and cause a net magnetomotive force in adirection opposite said first direction to be applied to said secondflux path; means for controlling said core When in said second remanentcondition to assume said first remanent condition comprising a furtherwinding means efiective when energized to overcome said biasmagnetomotive force applied by said second bias winding and cause a netmagnetomotive force in a direction opposite said first direction to beapplied to said third flux path; and sense winding means inductivelyassociated with at least one of said flux paths.

8. The invention as claimed in claim 7 wherein said first flux path isshorter than said second fiux path, said second flux path is shorterthan said third flux path, and said third flux path is shorter than saidfourth flux path.

9. The invention as claimed in claim 8 wherein said winding meansembracing said second flux path comprises first and second half selectwindings each of which when energized is of itself insufficient tocontrol said core when in said first remanent condition to assume saidsecond remanent condition but both of which when energized coincidentlyare effective to control said core when in said first remanent conditionto assume said second remanent condition.

10. A magnetic memory device comprising a core of magnetic materialhaving first, second and third openings positioned through a portionthereof dividing said portion into first, second, third and fourthparallel flux paths, said core being capable of being caused to assume afirst remanent condition with fiux oriented in a first direction in aclosed fiux path extending around said core and including said first andsecond flux paths and a second remanent condition with fiux oriented insaid first direction in a closed flux path around said core andincluding said third and fourth flux paths, first and second biaswindings embracing said second and third flux paths respectively, afirst pair of half select drive windings each embracing said second fluxpath, a second pair of half select drive windings each embracing saidthird flux path, and a sense winding embracing at least one of saidparallel fiux paths.

11. A magnetic memory device comprising a core of magnetic materialhaving a portion thereof divided into a plurality of parallel fluxpaths, said core being capable of being caused to assume a firstremanent condition with flux oriented in a first direction in a closedflux path extending around said core and including a first one of saidplurality of parallel flux paths and a second remanent condition withiiux oriented in said first direction on a closed flux path extendingaround said core and including a second one of said plurality of fluxpaths, bias means adjacent said first and second parallel flux paths,respectively, for applying magnetomotive force in said first directionto at least a portion of each path, first and second input Winding meansinductively associated with said first and second parallel paths,respectively, each for applying magnetomotive force in a directionopposite said first direction to at least a portion of the associatedpath, and sense winding means embracing at least a portion of one ofsaid parallel flux paths.

12. In a magnetic memory device, a core of magnetic material having aportion thereof divided into first, second, third and fourth parallelflux paths, said core being capable of being caused to assume a firstremamint condition with flux oriented in a first direction in a closedflux path extending around said core and including said first and secondflux paths and a second remanent condition with flux oriented in anopposite direction in a closed flux path extending around said core andincluding said first and fourth fiux paths; means for nondestructivelyinterrogating the condition of said core comprising first winding meansembracing said second flux path effective when energized to applymagnetomotive force in said first direction to said second flux path, asecond winding means embracing said third flux path effective whenenergized to apply magnetomotive force in said first direction to saidthird flux path, and a sense winding embracing at least one of saidparallel flux paths.

13. The invention as claimed in claim 12 wherein said first windingmeans comprises first and second individual half select windings.

14. In a magnetic memory device, a core of magnetic material having afirst portion thereof divided into a plurality of parallel flux paths,said core being capable of being caused to assume a first remanentcondition with fiux oriented in one direcion in a closed flux pathextending around said core and including a first one of said pluralityof parallel fiux paths and with flux oriented in' a first local closedflux path extending within said first portion of said core and includingportions of two of said plurality of parallel flux paths other than saidfirst one of said parallel flux paths, said core being capable of beingcaused to assume a second remanent condition with flux oriented in aclosed flux path extending around said core and including a second oneof said plurality of parallel flux paths and with flux oriented in asecond local closed flux path extending within said first portion ofsaid core and including portions of two of said plurality of flux pathsother than said second one of said parallel flux paths; means fornondestructively interrogating said core comprising first and secondwinding means each embracing a different one of said plurality ofparallel flux paths and effective when alternately energized when saidcore is in said first remanent condition to alternately reverse the fluxin said first local flux path, said first and second winding means beingineffective when said core is in said second remanent condition toreverse the fiux in any of said flux paths, and a sense windinginductively associated with said first local flux path.

15. A binary storage device comprising a magnetic core having first andsecond portions, said first portion being divided into a plurality ofparallel flux paths, said core being capable of being caused to assume afirst remanent condition with fiux oriented in a first direction in aclosed fiux path extending around said core and including one of saidplurality of parallel flux paths and a second remanent condition withflux oriented in a second direction in a closed fiux path extendingaround said core and including one of said plurality of parallel fluxpaths, input winding means embracing said second portion of said corefor selectively causing said core to assume said first and secondremanent conditions; means for nondestructively interrogating the stateof said core comprising first and second winding means each embracingonly one of said plurality of parallel flux paths and each effectivewhen energized to apply magnetomotive force in said first direction tosaid embraced path, and sense winding means inductively associated withat least one of said plurality of flux paths.

16. In a magnetic memory device, a core of magnetic material havingfirst and second portions, said first portion being divided into atleast first and second parallel flux paths, first winding meansembracing magnetic material in said second portion of said core forselectively establishing first and second remanent conditions of fluxorientation in first and second directions in a closed flux pathextending around said core and including magnetic material in each ofsaid first and second portions; and means for interrogating thecondition of said core comprising a second winding means embracing onlymagnetic material in said first parallel flux path in said first portion of said core, said second winding means being arranged so that whenenergized it applies magnetomotive force in the same direction to all ofthe magnetic material it embraces, a third winding means embracing onlymagnetic material in said second parallel flux path in said firstportion of said core, said third winding means being arranged so thatwhen energized it applies magnetomotive force in the same direction toall of the magnetic material which it embraces, first pulse meanscoupled to said second winding means for applying thereto a pulseeffective to cause magnetomotive force in said first direction to beapplied to the magnetic material embraced by said second winding means,second pulse means coupled to said third winding means for applyingthereto a pulse efiective to cause magnetomotive force in said firstdirection to be applied to the magnetic material embraced by said thirdwinding means, and sense winding means inductively associated with saidfirst portion of said core.

17. A binary storage device comprising a magnetic core having a firstportion thereof divided into at least first, second and third parallelflux paths, said core being capable of being caused to assume a firstremanent condition with flux oriented in one direction in a closed fluxpath extending around said core and including said first parallel fluxpath and a second remanent condition with flux oriented in one directionin a closed flux path extending around said core and including saidfirst flux path, first and second winding means for applyingmagnetomotive force to said core, said first winding means embracingmagnetic material in said first flux path only and wound so that whenenergized it is effective to apply magnetomotive force in the samedirection to all of the magnetic material it embraces, said secondwinding means embracing magnetic material in one of said second andthird flux paths and wound so that when energized it is effective toapply magnetomotive force in the same direction to all of the magneticmaterial it embraces, and sense winding means inductively associatedwith at least one of said first, second and third flux paths.

18. The'invention as claimed in claim 17 wherein said first windingmeans comprises first and second individual half select windings.

19. The invention as claimed in claim 17 wherein said first windingmeans includes a bias winding wound in a first sense and a furtherwinding wound in a sense opposite said first sense.

20. In a magnetic memory array, a plurality of binary storage coresconnected in coordinate rows and columns, each said storage core havinga first and second portion, said second portion of each core beingdivided into at least first, second and third parallel flux paths, eachof said cores being capable of being caused to assume a first remanentcondition with flux oriented in a first direction in a closed flux pathextending around said core and including said first flux path and asecond condition of flux remanence with flux oriented in an oppositedirection in a closed flux path extending around said core and includingsaid first flux path, coordinate half select write windings embracingsaid first portion of said cores for selectively causing said cores toassume said first and second remanent conditions; a plurality of pairsof coordinate half select setup drive windings, each pair embracing onlysaid first flux path of an associated one of said cores, forcoincidently applying magnetomotive force in said first direction tosaid embraced path; a plurality of series connected read windings, eachembracing said second fiux path only of an associated one of said cores,for applying magnetomotive force in said second direction to saidembraced path, and a sense winding embracing at least one of said first,second and third flux paths of each of said cores.

References Cited in the file of this patent The Transfiuxor (Rajchman),Proceedings of the IRE, vol. 44, issue 3, pp. 321-322, March 1956. (Copyin Div. 42.)

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent N0},- 2898,58l August 4, 1959 Frederick L. Post It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 16, line l8 for "first", first occurrence, read. third Signedand, sealed this 9th day of May 1961.

(SEAL) Attest:

ERNEST W SWIDER DAVID L LADD Attesting Officer Commissioner of PatentsUNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No; 2898581 August 4, 1959 Frederick L. Post It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 16, line 18, for "first", first occur-Pence, readthird Signed andsealed this 9th day of May 1961o (SEAL) Attest:

ERNEST W; SWIDER DAVID LADD Attesting Officer Commissioner, of Patents

